High‐quality Pr2O3 high‐k thin films with very promising electrical properties have been prepared by metal–organic chemical vapor deposition on Si(100) substrates. The most critical factor for selective and reproducible Pr2O3 film formation is the oxygen partial pressure in the reaction chamber. X‐ray (see Figure) and transmission electron microscopy diffraction patterns show that the oxide layer grows with a hexagonal random structure.

ExperimentalMaterials Synthesis: The SBA-15 template was prepared by adding 4.0 g tri-block copolymer poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (EO 20 PO 70 EO 20 ) to a solution of 25 g (35 wt.-%) HCl and 125 g water under stirring. After stirring for 2 h, the copolymer was completely dissolved, after which 8.6 g TEOS was added. Following continuous stirring for 20 h at 35 C, the reaction mixture was transferred to a Teflon-lined autoclave and heated at 100 C for 24 h. The resulting product was obtained by filtration, washed repeatedly with a large amount of water, air-dried at room temperature, and calcined at 500 C for 6 h to remove the surfactant. The calcined SBA-15 was used as template for the preparation of mesoporous carbon CMK-3 by CVD as follows: 0.3 g of calcined SBA-15 was placed in an alumina boat and inserted into a flowthrough tube furnace. Under a flow of nitrogen saturated with styrene vapor at room temperature, the temperature of the furnace was increased, at a ramp rate of 20 C min ±1 , to the final pyrolysis/carbonization temperature (in the range 850±1050 C) and maintained for 3 h under the styrene-saturated nitrogen atmosphere. The furnace was then cooled to room temperature and the resulting SBA-15/carbon mesophase was thoroughly washed with hydrofluoric acid (HF) to etch out the silica. For comparison we also prepared a CMK-3 sample via liquid impregnation (designated CMK-3I) using the method of Jun et al. [4]. Sucrose was used as carbon source and carbonization was performed at 900 C for 7 h [4]. The mesoporous carbon was then recovered by etching the silica in HF. We also prepared CMK-3 samples using other carbon sources, e.g., acetonitrile.Characterization: Powder XRD analysis was performed using a Philips 1830 powder diffractometer with Cu Ka radiation (40 kV, 40 mA). Nitrogen sorption isotherms and textural properties of the materials were determined at ±196 C using nitrogen in a conventional volumetric technique by a Coulter SA3100 sorptometer. Before analysis, the samples were oven dried at 150 C and evacuated for 12 h at 200 C under vacuum. The surface area was calculated using the Brunauer±Emmett±Teller (BET) method based on adsorption data in the partial pressure (P/P 0 ) range 0.05±0.2, and the total pore volume was determined from the amount of the nitrogen adsorbed at P/P 0 » 0.99. The micropore surface area and micropore volume were obtained via t-plot analysis. SEM images were recorded using a JEOL JSM-820 scanning electron microscope. Samples were mounted using a double-sided conductive carbon sticky tape. A thin (ca. 10 nm) coating of gold sputter was deposited onto the samples to reduce the effects of charging. Thermogravimetric analysis of the silica/carbon (i.e., SBA-15/CMK-3) composite materials was performed using a Perkin Elmer Pyris 6 TG analyzer (heating rate of 20 C min ±1 ) in static-air conditions. The field of microelectronics has developed rapidly over the last fifteen years, and its evolution is documented by the contin...

YAlO3 thin films doped with different amounts of Er3+ have been grown directly onto (110) SrTiO3 substrate using the metal-organic chemical vapor deposition method (MOCVD). X-ray diffraction patterns and the rocking curve of the (002) reflection point to the growth of <001>-oriented YAlO3 phase. Piezo-spectroscopic (PS) biaxial calibration was performed on two luminescence bands, related to transitions from the (4)S3/2 excited state, using a specially designed ball-on-ring loading jig. Such a PS calibration allowed us to retrieve the rate of wavelength shift with stress without separating the grown film from the substrate. The outcome of the PS calibration has been applied to build up in the field emission scanning electron microscope (FEG-SEM) high-resolution maps of the residual stress field developed in the film. Results indicate that the residual stress in Er3+:YAlO3 films were compressive in nature and increased with increasing Er3+ dopant concentration.

No abstract

No abstract